Japanese Patent Application Laid-Open No. 9-217613, for example, discloses a controller that controls an opening and closing operation of an intake valve of an engine. This controller employs an electromagnetic actuator and adjusts a current supplied to the electromagnetic actuator according to an operating state of the engine so as to perform the control. This controller also comprises, for example, an engine parameter detection sensor, an arithmetic operation circuit for calculating a current supplied to the electromagnetic actuator based on an engine parameter and designating a current value to be supplied, and a drive circuit for driving the electromagnetic actuator according to the designated current value to be supplied.
In the above-mentioned conventional technology, engine speed data obtained from, for example, a crank angle sensor may have an abnormally large value due to an influence of noise. Further, when the arithmetic operation circuit is composed of a microcomputer, an error signal indicating an error of the microcomputer itself may be issued. Further, when a magnetic sensor is disposed in the electromagnetic actuator, an abnormal signal may be issued from the magnetic sensor.
When a so-called signal system including the sensor system and the arithmetic operation system is in an abnormal state, a problem arises in that opening and closing of the intake valve is not appropriately controlled by the electromagnetic actuator. Further, timing at which the intake valve is opened and closed, lift amount thereof, and the like are set by a data map using an engine speed as a parameter. However, since engine speed (hereinafter, “engine speed”) obtained when a crank angle changes at a very slow speed at the start up of the engine, and the like, is excessively low, there is a problem in that an appropriate map value cannot be obtained.
The present invention has been achieved in order to solve the above problems. It is an object of this invention to provide a controller for controlling opening and closing of an intake valve of an engine capable of maintaining an engine operation even when a signal system is abnormal or even when an engine speed is in a non-normal state.